Methods and systems for turbulent, corrosion resistant heat exchangers

ABSTRACT

Disclosed are various turbulent, corrosion-resistant heat exchangers used in desiccant air conditioning systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from the following applications: (1)U.S. Provisional Patent Application No. 61/658,205 filed on Jun. 11,2012 entitled METHODS AND SYSTEMS FOR TURBULENT, CORROSION RESISTANTHEAT EXCHANGERS; (2) U.S. Provisional Patent Application No. 61/729,139filed on Nov. 21, 2012 entitled METHODS AND SYSTEMS FOR TURBULENT,CORROSION RESISTANT HEAT EXCHANGERS; (3) U.S. Provisional PatentApplication No. 61/731,227 filed on Nov. 29, 2012 entitled METHODS ANDSYSTEMS FOR TURBULENT, CORROSION RESISTANT HEAT EXCHANGERS; (4) U.S.Provisional Patent Application No. 61/736,213 filed on Dec. 12, 2012entitled METHODS AND SYSTEMS FOR TURBULENT, CORROSION RESISTANT HEATEXCHANGERS; (5) U.S. Provisional Patent Application No. 61/758,035 filedon Jan. 29, 2013 entitled METHODS AND SYSTEMS FOR TURBULENT, CORROSIONRESISTANT HEAT EXCHANGERS; and (6) U.S. Provisional Patent ApplicationNo. 61/789,357 filed on Mar. 15, 2013 entitled METHODS AND SYSTEMS FORTURBULENT, CORROSION RESISTANT HEAT EXCHANGERS, each of which is herebyincorporated by reference.

BACKGROUND

The present application relates generally to the use of liquiddesiccants to dehumidify and cool (and in some cases humidify and heat)an air stream entering a space. More specifically, the applicationrelates to the use of micro-porous and other membranes to separate theliquid desiccant from the air stream wherein the fluid streams (air,cooling or heating fluids, and liquid desiccants) are made to flowturbulently so that high heat and moisture transfer rates between thefluids can occur. The application further relates to corrosion resistantheat exchangers between two or three fluids. Such heat exchangers canuse gravity induced pressures (siphoning) to keep the micro-porousmembranes properly attached to the heat exchanger structure.

Liquid desiccants have been used in parallel to conventional vaporcompression HVAC equipment to help reduce humidity in spaces,particularly in spaces that either require large amounts of outdoor airor that have large humidity loads inside the building space itself.Humid climates, such as for example Miami, Fla. require a large amountof energy to properly treat (dehumidify and cool) the fresh air that isrequired for a space's occupant comfort. Conventional vapor compressionsystems have only a limited ability to dehumidify and tend to overcoolthe air, oftentimes requiring energy intensive reheat systems, whichsignificantly increase the overall energy costs because reheat adds anadditional heat-load to the cooling coil. Liquid desiccant systems havebeen used for many years and are generally quite efficient at removingmoisture from the air stream. However, liquid desiccant systemsgenerally use concentrated salt solutions such as solutions of LiCl,LiBr or CaCl₂ and water. Such brines are strongly corrosive, even insmall quantities so numerous attempt have been made over the years toprevent desiccant carry-over to the air stream that is to be treated.One approach—generally categorized as closed desiccant systems—iscommonly used in equipment dubbed absorption chillers, places the brinein a vacuum vessel, which then contains the desiccant and since the airis not directly exposed to the desiccant; such systems do not have anyrisk of carry-over of desiccant particles to the supply air stream.Absorption chillers however tend to be expensive both in terms of firstcost and maintenance costs. Open desiccant systems allow direct contactbetween the air stream and the desiccant, generally by flowing thedesiccant over a packed bed similar to those used in cooling towers.Such packed bed systems suffer from other disadvantages besides stillhaving a carry-over risk: the high resistance of the packed bed to theair stream results in larger fan power and pressure drops across thepacked bed, requiring thus more energy. Furthermore, thedehumidification process is adiabatic, since the heat of condensationthat is released during the absorption of water vapor into the desiccanthas no place to go. As a result, both the desiccant and the air streamare heated by the release of the heat of condensation. This results in awarm, dry air stream where a cool dry air stream was required,necessitating the need for a post-dehumidification cooling coil. Warmerdesiccant is also exponentially less effective at absorbing water vapor,which forces the system to supply much larger quantities of desiccant tothe packed bed, which in turn requires larger desiccant pump power sincethe desiccant is doing double duty as a desiccant as well as a heattransfer fluid. The larger desiccant flooding rate also results in anincreased risk of desiccant carryover. Generally, air flow rates need tobe kept well below the turbulent region (at Reynolds numbers of lessthan ˜2,400) to prevent carryover.

Membrane modules often suffer from problems wherein glue or adhesionlayers are stressed by temperature differences across the variouscomponents. This is particularly difficult in components that areoperating under high temperatures such as liquid desiccant regenerators.In order to inhibit cracking of the plastics or failures of the bonds oradhesives, a 2-part plate structure is disclosed that has a first partmade from a harder plastic (such as, e.g., ABS (Acrylonitrile butadienestyrene)) and a second part made from a compliant material (such as,e.g., EPDM (ethylene propylene diene monomer) rubber or Polyurethane).One advantage of this structure is that the compliant material easilyabsorbs the differences in expansion coefficients, while still providingfor fluid passages and other features such as edge seals for airpassages and turbulating features for those same air passages.

There thus remains a need for a system that provides a cost efficient,manufacturable and thermally efficient method to capture moisture froman air stream, while simultaneously cooling such an air stream and whilealso eliminating the risk of contaminating such an air stream.

Heat exchangers (mostly for 2 fluids) are very commonly used in manyapplications for heat transfer and energy recovery. Most heat exchangersare constructed out of metals such as copper, stainless steel andaluminum. Generally speaking such heat exchangers incorporate featurethat attempt at disturbing the fluid flows in order to enhance the heattransfer between the fluid and the metal surfaces. Boundary layers onthe surface of the metals create larger resistances to heat transfer. Inquite a few applications, one or both of the fluids can be corrosive tothe commonly used metals. Surface coatings can help prevent corrosion,but tend to also have decreased heat transfer. Metals that are notsensitive to corrosion such as Titanium, are generally consideredexpensive to use and difficult to work with. Plastics can be used butthey oftentimes cannot withstand the operating pressures andtemperatures that are typically used for the fluids. There thus remainsa need for a cost-effective, corrosion resistant liquid to liquid heatexchanger.

SUMMARY

Provided herein are methods and systems used for the efficientdehumidification of an air stream using a liquid desiccant. Inaccordance with one or more embodiments the liquid desiccant is runningdown the face of a support plate as a falling film. In accordance withone or more embodiments, the liquid desiccant is covered by amicroporous membrane so that liquid desiccant is unable to enter the airstream, but water vapor in the air stream is able to be absorbed intothe liquid desiccant. In some embodiments, the air stream contains aturbulator: a material or feature that induces turbulence in the airflow so that the air does not become laminar over the surface of thedesiccant. In some embodiments, the turbulator is a plastic nettingmaterial. In some embodiments, the turbulator is a series of plasticwires that span across the air flow. In some embodiments, the membraneis a bi-axially stretched polypropylene membrane. In some embodiments,the liquid desiccant is running through a wicking material such as afabric or a thin screen material, wherein the fabric or screen materialsets a fixed distance between the support plate and membrane. In someembodiments, the screen material or fabric provides a mixing orturbulence to the desiccant so that fresh desiccant is brought close tothe membrane and spent desiccant is removed from the surface near themembrane. In some embodiments, the membrane is bonded through the screenor wicking material onto a support plate. In some embodiments, thesupport plate is a somewhat thermally conductive rigid plastic such as afiberglass reinforced plastic. In some embodiments, the support plate iscooled on the opposite side by a cooling fluid. In some embodiments, thecooling fluid is water or a water/glycol mixture. In some embodiments,the cooling fluid is running through a plastic mesh wherein the plasticmesh sets the distance between the support plate and a second supportplate and wherein the cooling fluid is made to become turbulent by themesh. In some embodiments, the mesh is a dual plane diamond plasticmesh. In some embodiments, the second support plate is bonded to thefirst support plate by a series of adhesive dots so that the plates donot bulge out due to the cooling fluid pressure. In some embodiments,the support plates are formed so that similar features of the diamondmesh are formed directly into the support plate. In some embodiments,the support plate is joined to a second support plate wherein bothplates contain features that achieve the functions of the diamond mesh:setting a fixed distance between the two support plates and creating aturbulent mixing cooling fluid flow. In some embodiments, the featuresof the wicking material or screen material on the desiccant side arealso incorporated into the support plates. In some embodiments, the gluedots on either or both the desiccant or cooling fluid side are replacedby thermal bonding, ultrasonic bonding, or some other bonding method toconnect to a membrane or to a second support plate. In some embodiments,the support plate itself contains an adhesive in the plastic that isactivate by some process, either by heat, or ultrasonic sound ormicrowaves or some other suitable method.

In some embodiments, the diamond mesh comprises a co-extruded plasticand an adhesive. In some embodiments, the plastic is coated with anadhesive in a separate process step. In some embodiments, the secondsupport plate provides a second screen and mesh and faces a second airgap containing a second air turbulator. In some embodiments, a soconstructed membrane plate assembly is provided with multiple liquidsupply- and drain ports so that uniform liquid distribution is achievedacross the surfaces of the membrane and support plates. In someembodiments, the ports are reconfigurable so that the air can bedirected in either a horizontal or vertical fashion across themembranes. In some embodiments, the air turbulator is constructed sothat it is effective for either horizontal or vertical air flow. In someembodiments, the liquid ports can be configured so that the coolingfluid is always flowing against the direction of the air flow so that acounter-flow heat exchange function is obtained. In some embodiments,the drain ports to the plate are constructed in such a way as to providea siphoning of the leaving liquids thereby creating a negative pressurebetween the support plates with respect to atmospheric pressure and anegative pressure between the support plate and the membrane ensuringthat the membrane stays flat against the screening material or wickingfabric. In some embodiments, the main seals in between the supportplates are constructed so as to provide a self-draining function so noliquids stay inside the membrane plate system. In some embodiments, suchself-draining seals create separate areas for the liquid desiccants andfor the cooling fluids so that a leak in one of the seals will notaffect the other fluid. In other embodiments the support plate is onlypartially covered by a membrane, thereby providing an additional areafor sensible only cooling. In some embodiments the partially coveredsupport plates encounter a vertical air flow and an also vertical heattransfer fluid flow directed in a direction opposite or counter to theair flow. In some embodiments the partially covered support platesupports a horizontal air flow and an also horizontal heat transferfluid flow directed primarily in a direction counter to the air flow. Insome embodiments the glue dots are minimized to take advantage of thesiphoning of the liquids leaving the channels of the plate therebymaximizing the available membrane area.

Systems and methods are provided wherein the membrane plate assembliesdescribed in the previous section are connected by a pliable spacer. Insome embodiments, the spacer is made from a rubber material such asEPDM. In some embodiments, the spacer has annular seals providingseparation between the liquids and sealing the spacer to the surface ofthe support plate. In some embodiments, the spacer is fully coated withan adhesive. In some embodiments, the spacer also contains features tosupport the air netting turbulator. In some embodiments, the spacercontains features that keep the air turbulator under tension. In someembodiments, the spacer is shaped so that it also provides a wall tochannel the air stream in a proper direction. In some embodiments, therubber material is over-molded on the support plate. In someembodiments, the spacer and the air netting turbulator form a singlemanufactured component. In some embodiments, the air netting and spacerare separate components. In some embodiments, the air netting turbulatorcontains support structures designed to hold a membrane in a fixedlocation. In some embodiments, the air netting turbulator, membranes andsupport plates, with or without cooling fluid centers are stackedwherein the spacer and support netting eliminate the need for adhesives.In some embodiments, the plates, support structures and spacers are madefrom flexible materials so that the structures can be rolled into acylindrical shape. In some embodiments a force is applied to thecompliant spaces to adjust and air gap between membrane plates. In someembodiments the force is applied in a larger amount near one end of themembrane plate and a smaller amount near the opposite end of a membraneplate, resulting in an air gap that is smaller on one end as it is onthe opposite end. In some embodiments the variable air gap is matched tothe shrinkage or expansion of air in the channel. In some embodimentsthe variable air gap is dynamically adjusted to optimize betweenmembrane efficiency and air pressure drop in the channel. In someembodiments the spacers are made to be wider on one side of a membranemodule and narrower on the opposite side of the membrane module. In someembodiments the air gaps are so adjusted to match the expansion orcontraction of the air in between the membrane plates.

In some embodiments, a series of so constructed plates and spacers asdiscussed above are placed in a block. In some embodiments, the blockcontains a larger series of plates. In some embodiments, the block canbe reconfigured so that the air stream enters from either a verticalaspect or a horizontal aspect into the plates. In some embodiments, theports in the block can be reconfigured so that the cooling fluid isalways directed against the flow of the air stream. In some embodiments,the cooling fluid is replaced by a heating fluid. In some embodiments,the heating fluid is used to evaporate water vapor from the desiccantinto the air stream through the membrane rather than absorbing watervapor into the desiccant when the fluid is cool.

In accordance with one or more embodiments, air treatment modules aredisclosed comprising alternating rigid and flexible materials. In someembodiments, the rigid element uses a liquid distribution header at thetop of the module and a similar liquid distribution header at the bottomof the module, connected by two support plates. In some embodiments, theheaders are split to supply two fluids to a series of membranes. In someembodiments, one set of membranes receives fluids from one portion ofthe top header, while a second set of membranes receives fluids from asecond portion of the header. In some embodiments, the headers are madewith a flexible material such as, e.g., EPDM rubber, while the supportplates are made with a more rigid material such as, e.g., ABS or PET. Insome embodiments, the support plates are doped with fire retardingadditives or thermally conductive additives. In some embodiments, thesupport plates have holes for fluid supply and fluid drain incorporatedin them. In some embodiments, the support plates have a series ofmembranes attached over them. In some embodiments, the membranes areconnected to the support plate using an adhesive. In some embodiments,the adhesive is contained in a screen material that also providesturbulent mixing of the liquid. In some embodiments, the adhesive isconnected through a thin screen material that provides turbulent mixingof the fluid. In some embodiments, the turbulating features areintegrated into the support plate. In some embodiments, the supportplates have turbulating features on either side of them. In someembodiments the screen material is formed in such a way as to provide asurface turbulence in the air stream. In some embodiments the membraneis formed in such a way as to provide turbulence in the air stream. Insome embodiments the membrane is adhered over the features in the screenmaterial so that the combination creates turbulence in the air stream.In some embodiments the support plate has added features that createridges over which the screen material and membranes are formed to createturbulence in the air stream. In some embodiments, the air gaps betweenthe support plates are filled with a flexible structural material tosupport the membranes. In some embodiments, the flexible structuralmaterial provides an edge seal for the air gaps. In some embodiments,the flexible structural material provides turbulence to the air stream.In some embodiments the turbulating feature is located on the surface ofthe membranes. In some embodiments the turbulating feature is located inthe middle of the air gap. In some embodiments, the flexible structuralmaterial provides liquid passages to the supply liquids or drain liquidsfrom the membranes. In some embodiments the turbulator has walls thatare sloped at an angle to the air stream. In some embodiments theturbulator walls that are alternatingly sloped at opposite angles to theair stream. In some embodiments the turbulator walls get smaller in thedownstream direction. In some embodiments the turbulator has a secondarystructure that contains walls that are directing the air stream backtowards the opposite direction from the primary wall structure in such away that a rotation in the air stream is enhanced. In some embodimentsthe combination of primary and secondary walls results in acounter-rotating air stream down an air channel.

Methods and systems are also provided wherein several 2-part rigid andflexible membrane plate components are stacked to obtain a membrane airtreatment module. In some embodiments, such an air treatment modulereceives a primary air flow in a primarily vertical orientation and asecondary air flow in a primarily horizontal orientation. In someembodiments, the vertical air flow is exposed to one set of membranes,whereas the horizontal air flow is exposed to a second set of membranes.In some embodiments, the one or both sets of membranes are replaced witha flocking, fabric, netting or other hydrophilic material on the surfaceof the membrane support plate. In some embodiments, the primary air flowis exposed to one fluid through one set of the membranes, and thesecondary air flow is exposed to a second fluid through the other set ofmembranes. In some embodiments, the first fluid is a desiccant solutionsuch as LiCl and water, CaCl₂ and water or other suitable liquiddesiccant. In some embodiments, the second fluid is water or seawater orwaste water or other inexpensive water source. In some embodiments, thefluids are the same. In some embodiments, the primary and secondary airchannels are both oriented to be generally horizontal. In someembodiments, both the channels expose air to the same liquid behind aseries of membranes.

In some embodiments, the primary air channel is generally horizontalwherein the air is exposed to a liquid desiccant and wherein a portionof the thus treated is diverted to the secondary channel wherein thetreated air is mixed with a secondary air stream and exposed to adifferent liquid such as water. In some embodiments, the water isreplaced with seawater or wastewater. In some embodiments, the divertedair flow is adjustable to that the amount of diverted air can be varied.In some embodiments, the diverted air flow is adjustable to vary themixture ratio between the diverted air and the secondary air stream. Insome embodiments the diverted air flow is directed to near the rearentry of the primary air flow channels where the effect of the driedprimary air has a larger cooling effect in the secondary air stream thanif the air flow was directed to near the rear exit of the primary airflow channels.

Methods and systems are provided wherein two fluids exchange heatbetween them through a series of parallel plates. In some embodiments,the fluids are corrosive fluids. In some embodiments, the fluidsfunction as desiccants. In some embodiments, the desiccants containLiCl, CaCl₂, Ca(NO₃)₂, LiBr and water or other salt solutions. In someembodiments, one liquid is hot and the other liquid is cold. In someembodiments, the parallel plate structure comprises plates with anadhesive edge seal. In some embodiments, the plates are made of aplastic material. In some embodiments, the plastic material is afiberglass reinforced plastic, or Poly-Ethylene-Terephthalate (PET) orother plastic material. In some embodiments, the plate material is asheet of corrosion resistant material such as Titanium. In someembodiments, the plate material is a thermally doped engineeringplastic. In some embodiments, the dopants are ceramics such as disclosedin U.S. Patent Application Publication No. 2012/0125581. In someembodiments, the space between the plates is filled with a dual planardiamond extruded mesh. In some embodiments, the mesh provides a fixeddistance between the plates while allowing for passage of the fluids. Insome embodiments, the mesh creates turbulence in the fluids. In someembodiments, the mesh comprises a co-extruded plastic and an adhesive.In some embodiments, the plastic is coated with an adhesive in aseparate process step. In some embodiments, the adhesive comprisesadhesive dots that reach though the mesh between two sheets of platematerial. In some embodiments, the seals between the parallel plates aremade out of an adhesive. In some embodiments, the adhesive is a 3M 550or 5200 adhesive or a similar polyurethane adhesive. In someembodiments, the seals are shaped so as to create opposing flow profilesbetween opposing plates.

Membrane modules often suffer from problems wherein glue or adhesionlayers are stressed by temperature differences across the variouscomponents. This is particularly difficult in components used for theregeneration of the desiccant, since many common plastics have highthermal expansion coefficients. Oftentimes specialty high-temperatureplastics are employed that are expensive to use in manufacturing.Bonding large surface areas together also creates problems with theadhesion and can cause stress fractures over time. Potting techniques(typically a liquid poured plastic) have some resilience if the pottingmaterial remains somewhat compliant even after curing. However thesystems and methods described herein are significantly more resistant toexpansion caused by high temperatures, which keeping the manufacturingprocess simple and robust.

Furthermore, a problem when building conditioner and regenerator systemsfor 2-way liquid desiccants is that it is hard to design a system thatprovides uniform desiccant distribution on both sides of a thin sheet ofplastic support material. The systems and methods described herein showa simple method for exposing an air stream to a series of membranescovering the desiccant.

Methods and systems are provided herein wherein a 2-way membrane moduleutilizes a set of refrigerant lines to actively cool a desiccant flowingbehind a series of membranes. Flowing a desiccant directly over metaltubes such as copper refrigerant lines is problematic since thedesiccants (typically Halide salts) are highly corrosive to most metals.Titanium is a possible exception but is cost prohibitive to employ.Rather than using Titanium piping, systems and methods described hereinshow a plastic support sheet that is wrapped around copper refrigerantlines thereby achieving direct cooling of the desiccant rather thanusing an indirect evaporative channel for cooling of the desiccant. Insome embodiments, the refrigerant is running in copper tubing. In someembodiments the copper tubing is wrapped by a plastic support sheet. Insome embodiments the plastic support sheet forms the support structurefor a membrane, which in turn contains a desiccant fluid.

In no way is the description of the applications intended to limit thedisclosure to these applications. Many construction variations can beenvisioned to combine the various elements mentioned above each with itsown advantages and disadvantages. The present disclosure in no way islimited to a particular set or combination of such elements.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a prior art 3-way, cross-flow heat exchanger thatemploys a double U-shaped cooling liquid path, a falling film desiccantflow (downward) and a horizontal air flow.

FIG. 2 illustrates a detail of FIG. 1.

FIG. 3 shows a plastic two-way liquid to liquid heat exchanger as shownin US Patent Application Publication No. 2012/0125581.

FIG. 4 shows a 3-way reconfigurable counter-flow heat exchanger inaccordance with various embodiments set up with vertical air flow(downward), vertical cooling fluid flow (upward) and a vertical fallingfilm desiccant (downward) behind a membrane.

FIG. 5 demonstrates a different configuration of the heat exchanger fromFIG. 4 set up as a cross-flow system with horizontal air flow, avertical cooling fluid flow (upward) and a falling film desiccant(downward) behind a membrane.

FIG. 6 shows the heat exchanger of FIG. 5 in a counter-flow setup againwith horizontal air flow, but with horizontal cooling fluid flow(against the direction of the air flow) and a falling film desiccant(downward) behind a membrane.

FIG. 7 shows a schematic flow diagram of the 3-way heat exchanger ofFIG. 4 wherein the fluids are collected through a gravity draincirculation system.

FIG. 8 shows a schematic flow diagram of the 3-way heat exchanger ofFIG. 5 wherein the fluids are collected through a gravity draincirculation system.

FIG. 9 shows a schematic flow diagram of the 3-way heat exchanger ofFIG. 6 wherein the fluids are collected through a gravity draincirculation system.

FIG. 10 shows a cross-sectional view of the individual plates thatprovide 3-way heat exchange between air, desiccant and a cooling fluid,including the materials that create turbulence in the air, desiccant andwater channels.

FIG. 11 demonstrates a siphoning drain for the 3-way heat exchangerplate of FIG. 10 which allows the membranes to stay flat against thesupport structure. One of the membranes has been removed for purposes ofillustration.

FIG. 12 illustrates a non-siphoning drain for the same 3-way heatexchanger but shows that the membrane bulges into the air gap. One ofthe membranes has been removed for purposes of illustration.

FIG. 13 illustrates an alternate orientation of the siphoning drain forthe 3-way heat exchanger plate of FIG. 10, which allows for an almosthorizontal, flat orientation of the 3-way heat exchanger plates.

FIG. 14 shows a spacer that is used between two membrane plates of FIG.600 with individual fluid seals for desiccant and cooling fluid.

FIG. 15 illustrates a spacer that is used between two membrane plates ofFIG. 10 with a full seal encompassing both the desiccant and coolingfluid.

FIG. 16 shows an embodiment of a spacer over-molded on each side of theindividual plates of FIG. 10 with an adhesive to make the finalconnection between the plates.

FIG. 17 shows an embodiment of a spacer over-molded on only one side ofthe individual plates of FIG. 10 with an adhesive to make the finalconnection between the plates.

FIG. 18 shows an embodiment of a set of spacers of FIG. 14 used toconnect a set of membrane plates as were shown in FIG. 10, wherein thespacers are of equal thickness creating uniform channel widths betweenthe membrane plates.

FIG. 19 shows an embodiment of a set of spacers of FIG. 14 used toconnect a set of membrane plates as were shown in FIG. 10, wherein thespacers are of unequal thickness creating varying channel widths betweenthe membrane plates.

FIG. 20 shows the 3-way heat exchanger of FIG. 4 with the front coverface plate removed so that the first air channel is visible.

FIG. 21 shows the 3-way heat exchanger of FIG. 20 with severaladditional membrane plates removed for purposes of illustration.

FIG. 22 shows the 3-way heat exchanger of FIG. 5 with the front coverface plate removed so that the first air channel is visible.

FIG. 23 shows the 3-way heat exchanger of FIG. 5 with several additionalmembrane plates removed for purposes of illustration.

FIG. 24 illustrates an alternate turbulator for the air channels shownin FIG. 21.

FIG. 25 illustrates an alternate turbulator for the air channels shownin FIG. 23.

FIG. 26 shows an exploded assembly drawing of a single membrane plate inaccordance with one or more embodiments.

FIG. 27 illustrates a seal and turbulator detail for the core of themembrane plate in accordance with one or more embodiments.

FIG. 28 illustrates the seal, turbulator and adhesive dots as anintegral unit.

FIG. 29 shows an alternate construction of the seal wherein thedesiccant and cooling fluids are in separate seal areas and wherein theseal is shaped in such a way as to be self-draining.

FIG. 30 shows the seal of FIG. 29 mounted against a thermally conductivecover plate with drain- and supply-holes for the fluids.

FIG. 31 shows the assembly of FIG. 30 with a turbulating mesh andadhesive dots installed in the middle of the cooling fluid area.

FIG. 32 illustrates the assembly steps from the assembly of FIG. 31through the final assembly of a single membrane plate and spacers.

FIG. 33 illustrates the assembly process of multiple membrane plates.

FIG. 34 illustrates a detail of FIG. 33.

FIG. 35 shows a set of surface turbulators in the prior art.

FIG. 36 illustrates a set of surface turbulators using a membrane andsupport structure as the means of creating turbulent flow.

FIG. 37 shows a turbulator that is able to generate a counter-rotatingflow in a narrow air channel.

FIG. 38 shows half-plate assembly with an over-molded spacer and amembrane attached in accordance with one or more embodiments

FIG. 39 shows and exploded view of the half-plate assembly of FIG. 38 inaccordance with one or more embodiments.

FIG. 40 illustrates how two half-plates are adhered to form a singlemembrane plate in accordance with one or more embodiments.

FIG. 41 shows an air-turbulating netting material that can also providemechanical support to the membrane structure.

FIG. 42 shows a detail of FIG. 41 wherein two membranes connected to two3-way membrane plates are supported by an air-turbulating netting.

FIG. 43 shows a similar detail of FIG. 42 wherein two membranesconnected to two 2-way membrane plates are supporting by anair-turbulating netting.

FIG. 44 shows an embodiment of an air turbulating netting wherein thenetting also incorporates support structures designed to keep membranesmechanically in place and wherein edge spacers are integrated to thedesign.

FIG. 45 shows how the air turbulating netting can support a membranestructure that is rolled into a cylindrical structure. Detail “A” showsa 2-way heat exchanger plate structure. Detail “B” shows a 3-way heatexchanger plate structure.

FIG. 46 shows how the air turbulating netting can support a flatmembrane structure for a 3-way heat exchanger plate structure.

FIG. 47 shows how the air turbulating netting can support a flatmembrane structure for a 2-way heat exchanger plate structure.

FIG. 48 shows a support plate that has been die-cut and thermoformed toincorporate features for cooling fluid and desiccant distribution.

FIG. 49 shows how the support plate from FIG. 48 can be joined withanother support plate from FIG. 48 to form a complete plate structure.

FIG. 50 illustrates how the two support plates from FIG. 49 are joinedto form a single plate in a transparent aspect.

FIG. 51 shows a detail of a corner of the support plate of FIG. 48.

FIG. 52 shows an arrangement of seals for the liquid desiccant, membraneand cooling fluids of FIG. 10.

FIG. 53 shows an alternate arrangement of seals wherein the desiccantruns behind a membrane in zone “A” and the zone “B” only providessensible cooling.

FIG. 54 shows an alternate arrangement of seals wherein the desiccantruns on a first section “A” of the membrane plate and there is nomembrane on a second section “B” of the membrane plate.

FIG. 55 shows a 2-way heat exchanger in accordance with one or moreembodiments.

FIG. 56 shows a cut-away detail of the 2 way heat exchanger at an oddlevel intersection.

FIG. 57 shows a cut-away detail of the 2 way heat exchanger at an evenlevel intersection.

FIG. 58 illustrates the assembly of a single plate of the two-way heatexchanger of FIG. 55.

FIG. 59 shows an odd-level plate assembly of the two-way heat exchanger.

FIG. 60 shows an even-level plate assembly of the two-way heatexchanger.

FIG. 61 illustrates a 2-part membrane plate assembly that utilizes aprimary air stream in a vertical orientation and a secondary air flow ina cross flow, horizontal orientation wherein the cross flow air streamprovides indirect cooling to the main air stream.

FIG. 62 shows the 2-part membrane plate assembly of FIG. 61 with anouter membrane removed for illustrative purposes.

FIG. 63 shows the rear-side of 2-part membrane plate assembly of FIG.61.

FIG. 64 shows a detail corner of FIG. 63.

FIG. 65 shows a different aspect of FIG. 64 with an inner membrane andair turbulator removed for clarity.

FIG. 66 shows an exploded view of the 2-part membrane plate assembly ofFIG. 61.

FIG. 67 shows a detailed aspect of FIG. 66.

FIG. 68 shows a cross-sectional view of the top of 2-part the membraneplate assembly of FIG. 61.

FIG. 69 shows a cross-sectional view of the bottom of the 2-partmembrane plate assembly of FIG. 61.

FIG. 70 shows a cross flow plate module utilizing multiple copies of the2-part membrane plate assembly from FIG. 61.

FIG. 71 shows the cross flow plate module of FIG. 70 integrated into anair treatment module wherein a portion of the primary supply air streamis diverted and mixed with the secondary cross flow air stream.

FIG. 72 illustrates the air treatment module of FIG. 71 with one sidecover removed for illustrating the ability to vary the amount of airfrom the main stream to be diverted to the cross flow air stream.

FIG. 73 shows a detail of FIG. 72.

FIG. 74 illustrates an alternate embodiment of the system of FIG. 71,wherein the air stream is directed to the top portion of the cross flowplate module.

FIG. 75 shows a 2-part module wherein one plate provides 4 flow pathsfor liquids to be exposed to an air stream and wherein the air stream isprimarily horizontal.

FIG. 76 shows an exploded view of the 2-part module of FIG. 75.

FIG. 77 shows a detail of the exploded view of FIG. 76.

FIG. 78 shows an air treatment module with horizontal air flow whereinthe air stream is exposed to liquids on each of the channels in themodule.

FIG. 79 shows the air treatment module of FIG. 78 with cover platesremoved.

FIG. 80 illustrates the air treatment module of FIG. 2000 wherein thesupport plate has been modified to accommodate a set of refrigerantlines flowing inside the support plate so that direct cooling of thedesiccant is provided.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 depicts a 3-way heat exchanger in the prior art wherein airenters a stack of vertical plates. The vertical plates have provisionsfor a cooling fluid 38 and are coated with a flocking material. A liquiddesiccant is applied to the flocking material that slowly falls down thesurface of the plate, while absorbing water vapor from the air streamand conducting heat from the condensation and air into the coolingfluid.

FIG. 2 shows a cross section of a plate of FIG. 1 in the prior artwherein the cooling fluid enters at location 34, flows down to thebottom location 38 and back up to the upper location 38. The fluid thenflows again to the bottom and back up to the exit port 36. The long,narrow passages in the fluid flow result in laminar fluid flows and, ascan be seen in the figure, the air flow entering at 10 is at rightangles to the cooling fluid flows.

FIG. 3 illustrates a 2-way heat exchanger wherein alternating patternsare applied to a series of plates. The patterns are meant to disturb(turbulate) the fluid flows. Oftentimes 2-way heat exchangers areconstructed using metals because high pressures and temperatures arecommon in 2-way heat exchangers. In order to accommodate corrosivefluids, Titanium heat exchangers can be employed, but Titanium isexpensive and generally hard to work with (drilling, welding etc.).Plastic heat-exchangers have been build and proposed but can usually notwithstand very high pressures or temperatures.

FIG. 4 shows a flexible, completely turbulent flow, corrosion resistant,self-draining, negative pressure, membrane protected, counter-flow 3-wayheat exchanger meant for capturing water vapor from and air stream whilesimultaneously cooling the air stream. The high temperature, highhumidity air stream 301 enters a series of membrane plates 303 that cooland dehumidify the air stream. The cool, dry, leaving air 302 issupplied to a space such as for example a space in a building. Adesiccant is supplied through supply ports 304. Two ports are providedon each side of the plate block structure 300. The supply ports arespaced apart in such a way as to provide a uniform desiccant film flowacross the membrane plates 303. The desiccant film falls through gravityand is collected at the bottom of the plate block 300 and exits throughthe drain ports 305. A cooling fluid (or heating fluid as the case maybe) is supplied through ports 306 at the bottom of the plate block 300.Again, the cooling fluid supply ports are spaced in such a way as toprovide uniform cooling fluid flow inside the membrane plates 300. Thecooling fluid runs upward inside the membrane plates 303 and leaves theplate block 300 through the ports 307. Front/rear covers 308 and sidecovers 309 provide structural support and thermal insulation and ensurethat air does not leave through the sides of the block.

FIG. 5 shows the plate block of FIG. 4 reconfigured in such a way theair stream now can enter the block in a horizontal orientation. The airenters at 401 and leaves the block at 402. Top and bottom covers 403ensure structural support and prevent air from leaking out of the topand bottom of the plate block.

FIG. 6 illustrates the plate block of FIG. 5 however the cooling fluidflow has been reconfigured so that the fluid enters on the right handside of the block at ports 306 on the bottom right and port 405 on thetop right. The fluid now leaves the block at ports 307 on the top leftand port 404 on the bottom left. As can be seen from the figure, thecooling fluid flows in the opposite direction to the air stream flow,resulting in better heat and moisture transfer between the air and thedesiccant and cooling water.

FIG. 7 illustrates a simplified fluid flow diagram corresponding to theplate block configuration of FIG. 4. The air stream flows over themembrane plate surface starting at point 501. The membrane plate 504 isconstructed as a hollow structure with fluid passages. The cooling fluidpump 507 pumps fluid 502 into the hollow plate where it is distributed.The fluid then runs upward and leaves at exit port 505. The fluid canenter the plate at more than one port to ensure uniform fluiddistribution as is shown in the figure. The drain 505 is constructed insuch a way as to create a siphoning effect when the liquid drains outinto the tank 509. This results in a slightly negative pressure in theplate structure. The negative pressure helps prevent the plate frombulging out. A typical plate height is 500 to 600 mm, with a typicalthickness of 3 mm and a width of 400 to 500 mm. When a plate is filledwith water, the hydraulic pressure can push the walls of the plate apartresulting in a narrowing of the air gaps between the plates and at worsta pinching off of the air gap altogether. The siphoning and negativepressure forces the plates inward rather than outward and the air gap isproperly maintained.

Similarly the desiccant 503 is pumped by pump 506 to the top of theplate where it runs down as a falling film on the outside surface of theplate. The liquid desiccant is contained to the surface of the plate bya thin, microporous membrane (not shown). The membrane forces the liquiddesiccant into a drain channel in the plate, and similar to the coolingfluid, the desiccant drains through a siphoning drain 510 into adesiccant tank 508. The siphoning effect is even more important on thedesiccant side of the system, since the membrane is typically very thin(around 20 μm) and thus can bulge into the air gap much more easily.

FIG. 8 illustrates the flow diagram corresponding to the plate blockconfiguration of FIG. 5. The air stream enters at 501 across the platesurface. The flows of the other flows of the cooling fluid and thedesiccant are unchanged from the flows in FIG. 7.

The use of dual ports allows one to reconfigure the system of FIG. 8into the system shown in FIG. 9 and supply cooling fluid to both the topand bottom of the plate, thereby turning the cooling liquid flow into acounter-flow to the air stream and significantly increasing theefficiency of the heat exchanger function of the membrane plate 504.Since building air conditioning systems are built to accommodate a widevariations of buildings and climates is advantageous to be able to flowair out of an air conditioning system in either a horizontal or verticalfashion, without significantly altering the efficiency of the heatexchanger. By being able to alter the flow pattern in the membraneplate, the plate retains optimum efficiency in either air floworientation.

FIG. 10 shows a cross-sectional construction detail of a single membraneplate assembly. Incoming air 601 is directed over two mesh-shaped,air-turbulators 602. The air-turbulators 602 can be constructed ofvarious inexpensive materials such as poly-propylene extruded plasticnetting or plastic lines, or other convenient materials. An example of anetting that can function as an air-turbulator is the blackpoly-propylene OB1200 netting made by Industrial Netting, 7681 SetzlerPkwy N. Minneapolis, Minn. 55445, USA. Since the membrane plates have amembrane 603 helps prevent liquids from entering the air stream, themembrane plates unlike systems without membranes, can accommodateturbulent air flows, since the turbulent flow is not able to knockdesiccant into the air stream. The air-turbulator can thus enhance heatand moisture transfer from the airstream into the liquid desiccantwithout running the risk of desiccant carry-over. The membrane is forexample the EZ2090 poly-propylene, microporous membrane manufactured byCelgard, LLC, 13800 South Lakes Drive Charlotte, N.C. 28273. Themembrane is approximately 65% open area and has a typical thickness ofabout 20 μm. This type of membrane is structurally very uniform in poresize and is thin enough to not create a significant thermal barrier. Theuniform pore size ensures that there are no areas or spots of liquiddesiccant breaking through the membrane. The open area allows for goodcontact between the air and the desiccant. However, the polypropylenehas a very low surface energy making it hard to bond to by conventionaladhesives. Heat-bonding is possible but carries risk of damage to themembrane by creating pin-holes. Also the membrane is typically not ableto withstand temperatures of much more than 90 C, which means thatthermal welding needs to be a well-controlled process. Another option isto bond the membrane 603 bonded by adhesive dots 607 to a thin,thermally conductive plastic sheet 609. The adhesive dots can forexample be adhesive 550 or 5200 manufactured by 3M Corp., 3M Center St.Paul, Minn. 55144-1000. These non-solvent based adhesives are able tomechanically “grab” the membrane structure and are thus able to adherewell to both the membrane 603 and the plate structure 609. The adhesivedots 607 are spaced about 2.5 cm apart in a pattern suitable to creategood adhesion across the entire face of the plate structure 609. Theplate structure 609 comprises a reinforced polymer such as a fiberglassreinforced plastic sheet, PET film or engineered plastic selected forrigidity and inertness to the desiccant solutions. The plate structure609 is typically a sheet roughly 450 mm wide, 600 mm high and 0.4 mmthick. The plate plastic can be thermally doped to enhance heat transferbetween the desiccant 606 and the cooling fluid 608. The adhesive dots607 are applied through a fine screen material 606. The screen material606 is for example a thin polypropylene screen XN 4900 manufactured byIndustrial Netting, 7681 Setzler Pkwy N. Minneapolis, Minn. 55445, USA.The screen 606 serves two major functions: it turbulates the desiccant610 as it is flowing down the surface of the support plate 609. It alsosets a fixed distance between the support plate 609 and the membrane603, which results in better desiccant distribution and an eventhickness of the desiccant film 610 as it is flowing down the supportplate 609. Rather than employing adhesive dots 607, it would be clear tothose skilled in the art that other methods of bonding the membrane tothe screen 606 and the support plate 609 can be devised, for example bycoating the screen 606 with an adhesive or by co-extruding the screen606 with an adhesive so that the screen 606 already contains an adhesivethat can be activated by heat or some other activation mechanism.

The desiccant enters the membrane plate through supply port 611, whichis offset horizontally from the membrane area as will be shown in FIG.26. The desiccant flows through the distribution header 604, which canbe manufactured using an adhesive seal or plastic part as will also beshown in FIG. 26. The distribution header 604 has a series of smallapproximately 0.5 mm holes 616, which ensure a generally even desiccantfilm distribution on the top of the support plate 609. The desiccantthen proceeds to flow turbulently through the screen 606. The membraneis adhered to the support plate through the adhesive dots 607 as well asadhered with an edge seal 617. The edge seal can either be made with anadhesive such as 3M 550 or 5200 mentioned earlier or with ahigh-temperature capable double sided adhesive tape such as 3MTMAdhesive Transfer Tape 950 3M Id: 70-0060-3055-8 as manufactured by 3MCorp. In either case, the desiccant reaches the bottom of the supportplate, and the bottom seal forces the desiccant into the support platedrain holes 619. The desiccant then proceeds to the drain port 614,where a siphoning drain 615 collects the desiccant into a tank (notshown).

A cooling fluid enters the cooling supply port 613. The cooling fluidenters a hollow area between the two support plates 609. The hollow areameasures approximately 550 mm×430 mm×2.5 mm thick. The hollow area iscompletely separated from the desiccant area by the seals 604. Thehollow area is also filled by a cooling-fluid turbulator 608. Thisturbulator 608 can comprise a coarse diamond shaped screen such as theXN 4700 diamond mesh manufactured by Industrial Netting, 7681 SetzlerPkwy N. Minneapolis, Minn. 55445, USA. The diamond mesh is a two-planarmaterial that serves two functions: it sets the distance between the twosupport plates 609 to a precisely controlled and uniform distance. Italso creates turbulence or stirring in the cooling fluid as it flowsthrough the hollow area, thereby efficiently absorbing heat from thesupport plates 609. The 2-planar diamond mesh has the advantage that itcontains enough variation in the wire thicknesses that it does notsignificantly obstruct liquid flow. The diamond structure alsodistributes the cooling fluid evenly in the hollow area with no inactiveflow areas that can result in uneven cooling performance of the membraneplate structure. Finally the support plates 609 are connected to eachother by additional adhesive dots 620 that can be made from similarmaterial to the adhesive dots 607. These additional adhesive dots ensurethat the plates stay uniformly connected to each other, even when thehollow area is filled with cooling fluid which will exert a force thatis separating the plates 609. The adhesive dots 620 are also placed in aregular pattern that ensures an even connection between the two plates,typically 2.5 cm apart so as to create proper support against the forceof the cooling fluid that fills the hollow area. Rather than employingadhesive dots 620, it would be clear to those skilled in the art thatother methods of bonding the support plates 609 to the turbulator mesh608 and the opposite support plate 609 can be devised, for example bycoating the mesh 608 with an adhesive or by co-extruding the mesh 608with an adhesive so that the mesh 608 already contains an adhesive thatcan be activated by heat or some other activation mechanism.

The membrane plate assembly of FIG. 10 thus has 3 turbulent fluid flowsin a counter-flow arrangement, is constructed with inexpensivematerials, is corrosion resistant and is easily manufactured. Themembrane plate is also easily reconfigurable to accommodate bothhorizontal and vertical air flow with the cooling fluid in acounter-flow arrangement. It is also possible to adhere the membrane603, screen 606, adhesive dots 607 and support plate 609 in aroll-to-roll process. In such a process the adhesives chosen might bedifferent or may be applied for example with a screen printing system.

FIG. 11 and FIG. 12 illustrate the effect that the desiccant pressurecan have on the shape of the very thin membrane 603. The liquiddesiccant enters the membrane plate structure at port 611. It flowsthrough a small port (not shown) into the fine screening material 606described earlier and then proceeds as a falling film through thescreening material 606. For ease of illustration only one of themembranes 603 is shown. Although adhesive dots 607 hold the membrane 603against the screening material 606, a backpressure can develop near thebottom of the membrane plate 701 that results in the membrane bulginginto the air-gap thereby reducing or cutting off air flow as shown inFIG. 12. In FIG. 11 a proper siphoning drain 614 has been attached,which allows the desiccant to be sucked down the drain 614 and into thecollection tank 508 resulting in a negative pressure in area 702. Thisin turn allows the membrane 603 to be pressed flat against the screeningmaterial 606. A non-siphoning drain such as shown in FIG. 12 willenhance the backpressure and result in bulging of the membrane. Theadvantage of using a siphoning drain is that it reduces the need foradhesive dots 607 between the membrane 603 and the support plate 609.

The siphoning drain is a unique feature that allows the desiccant plateto be used in almost horizontal orientation such as is shown in FIG. 13.The siphoning drain 614 collects liquid desiccant at the lower edge ofthe plate. The membranes in location 701 are kept flat against thescreening material 606 by the negative pressure. The siphoning featurecan also be used in the main water channel 608 which similarly reducesthe need for the adhesive dots 620 that connect the support plates 609.

FIG. 14 shows a spacer 750A that is used to connect two of the membranesupport plates 609 as was shown in FIG. 10. The spacer 750A is typicallymade from a slightly compliant rubber such as EPDM or other suitablematerial. The spacer provides two fluid connections. Connection 753 isused to provide or drain cooling fluid to/from the membrane plates shownin FIG. 10 and connection 755 is used for supplying or drainingdesiccant from the membrane plates. Either connection is surrounded by asealing material 752 and 754. The sealing material can be an adhesive ora separate sealing ring with adhesives on both sides of the ring such asa ring made from 3M VHB Adhesive Transfer Tape F9473PC or similarmaterial. The advantage of having two separate seals such as is shown inFIG. 14 is that if one of the seals develops a leak, the leak will notaffect the other seal. Aspect 757 shows a side orientation of the spacerconstruction with the seal 752 also visible as well as the two membranesupport plates 609.

FIG. 15 shows an alternate implementation of the spacer wherein thewhole spacer 750B has been coated by an adhesive 756. Aspect 758 againshows a side orientation of the space construction. It will be obviousto those skilled in the art that many variations and combinations ofseals and adhesives can be made suitable for connecting the membraneplates of FIG. 10.

FIG. 16 illustrates a side orientation embodiment wherein the EPDMmaterial 761 is over-molded on the support plate 609. An adhesive 760makes the connection between the two over-molded parts therebyconnecting the two membrane plates.

FIG. 17 shows an alternate embodiment wherein the over-molding 762 isapplied to only one of the two support plates 609.

FIG. 18 illustrates a use of the spacers 763 of FIG. 14 wherein thespacers all have equal thickness allowing even spacing between themembrane plates 764. The incoming air stream 765 is directed between thespacers 763 and gets treated in area 766 before exiting the plates 767.However the membrane plates 764 are treating the air stream. In coolingmode, when the membrane plates are low in temperature, the air stream iscontracting since it is being cooled and dehumidified simultaneously. Itcan be beneficial in that circumstance to apply forces 768 and 769 onthe plate assembly thereby reducing the air gap width between theplates, which the compliant EPDM spacers will allow. By reducing the airgap, the efficiency of cooling and dehumidification is increased.However, the air also will experience a larger resistance to flow in thechannels and therefore there will be a tradeoff between coolingefficiency and pressure drop. It will be clear to those skilled in theart that the forces 768 and 769 can be applied equally thereby resultingin a more even reduction of the air gap, or can be applied unevenlythereby reducing the air gap more at one side of the membrane platescompared to the other side of the plates. This can be advantageous tocompensate for the reduction on air volume. For example, air enteringthe membrane plates at a temperature of 35 C has a density of about 1.13kg/m³ and has a density of 1.20 kg/m³ at a leaving temperature of 20 C.This increase in density results in a reduction in surface velocity nearthe exit of the membrane plates. By reducing the air gap near the exitof the membrane plates (for instance by applying a larger force 768 nearthe exit of the membrane plates than the force 769 near the entrance ofthe membrane plates), the surface velocity of the air over the membranescan be held constant, which allows a more optimum efficiency along themembrane surface.

FIG. 19 shows an alternate embodiment of the membrane module of FIG. 18wherein the spacers 773 near the entrance of the membrane plates 764 aremade wider than the spacers 774 near the exit of the membrane plates.The warmer entering air 770 enters the membrane plates 764 and graduallyshrinks as it is being cooled by the membrane plates in air channel 771.The leaving air 772 has shrunk to a smaller size matching more closelyto the width of the spacers 774 near the exit of the membrane module. Itwill be clear by those skilled in the art that if the air is beingheated by the membrane module, as is the case if the module functions asa regenerator, the membrane plates may be arranged to increase their airgaps to accommodate the expanding air as it is moving through themembrane plates.

FIG. 20 now illustrates the plate block of FIG. 4 with the front coverface plate removed so that the first air gap and first membrane plateare visible. The four spacers 750A are shown to provide the fluidconnections to the first membrane plate 802. Also visible is the airturbulator 801, which as discussed earlier can be a series of plasticlines or a mesh material attached to the side cover plates 309 in such away as to sit in the middle of the air gap where the air flowobstruction has the greatest effect on turbulence.

FIG. 21 shows the plate block of FIG. 20 with multiple plates removed sothat fluid connection into the membrane plates 803 are visible. Thedesiccant is supplied through port 611 and drains out through port 614.The cooling fluid enters through port 613 and leaves through port 612.

FIG. 22 now illustrates the plate block of FIG. 5 with the front coverface plate removed so that the first air gap and first membrane plateare visible. The four spacers 750A are shown to provide the fluidconnections to the first membrane plate 902. Also visible is the airturbulator 901, which as discussed earlier can be a series of plasticlines or a mesh material attached to the top and bottom cover plates 403in such a way as to sit in the middle of the air gap where the air flowobstruction has the greatest effect on turbulence.

FIG. 23 shows the plate block of FIG. 22 with multiple plates removed sothat fluid connection into the membrane plate 903 are visible. Thedesiccant is supplied through port 611 and drains out through port 614.The cooling fluid enters through port 613 and leaves through port 612.

FIG. 24 illustrates an alternative air-mesh wherein the turbulence isprovided by horizontal plastic lines 1001 that obstruct the air in thegaps between the membrane plates. This embodiment is less flexiblebecause if the air flow direction is converted to a horizontal flow asis shown in FIG. 25 the wires 1002 need to be repositioned as well.

FIG. 26 illustrates an exploded view of an embodiment of the membraneplate as discussed in FIG. 10. A membrane 1101 has provisions 1106 forfluid passages cut into it, or the corners of the membrane can simply beremoved as shown at 1107. As discussed earlier, a glue- or tape seal1102 seals the edges of the membrane 1101 to the support plate 609. Ascreen material or wicking fabric 606 is adhered to the support plate609 with glue dots 607 as discussed earlier. The support plate 609 canbe made of various plastics such as fiberglass reinforced plastic orthermally doped engineering plastics. The support plate has provisionsfor fluids as well as a series of small desiccant supply holes 1108 anddesiccant drain holes 1103. The support plate 609 is in turn bonded to adiamond mesh 1105 with a main seal 604 surrounding it. The main seal 604provides liquid seal as well as confines the areas for cooling fluids,and desiccants. The cooling fluid turbulator 608 is also shown. As canbe seen from the figure, the system is symmetrical about the mean seal604 and cooling fluid turbulator 608. Therefore a second support plate609, screen 606 and membrane 1101 are adhered to the opposite side ofthe mean seal 604. Bonding four spacers 750A to the four corners of themembrane plate, allows for connection to the next membrane plate.Repeating the assembly of FIG. 26 allows for a multi-plate stack to bebuilt and eventually configured into a complete plate block.

FIG. 27 shows the mean seal 604, which as discussed before can be madeentirely from an adhesive or an injection molded plastic part with anadhesive covered surface. The main seal 604 creates areas for desiccantsupply 1201 and desiccant drainage 1202, which are separate from thecooling fluid area 1203. A diamond mesh turbulator 608 is placed in themiddle of the seal 604. The final assembly of the components is shown inFIG. 28, which also shows the pattern of adhesive dots 620 that are usedto bond the assembly to the 2 support plates that were shown in FIG. 26.

FIG. 29 shows an alternate seal arrangement to the arrangement from FIG.27. The cooling fluid seal 1301 is now distinctly a separate seal fromthe desiccant supply seal 1302 and the desiccant drain seal 1303. Theseals 1302 and 1303 form channels 1304 and 1305 that are shaped toenable the desiccant to drain easily. Similarly the cooling fluid seal1301 is shaped to enable the cooling fluid to drain easily. Thisself-draining feature makes draining the system for servicesignificantly easier and less messy. FIG. 30 shows the seal assembly ofFIG. 29 place on top of one of the support plates 609. As can be seenfrom the figure, the desiccant supply holes 1108 and drain holes 1103are placed on a horizontal line, whereas the seals are constructed withand angle with respect to the horizontal plane. As a result of the sealshape desiccant distribution at the top is uniform and the siphoning atthe bottom is enhanced. The holes 611, 612, 613 and 614 in the supportplate 609 are also shown and these are placed in the corner of the sealsso as to not to create a pocket where liquids can collect. FIG. 31finally shows the installation of the diamond mesh turbulator 608 andthe adhesive dots 620 that connect the two support plates 609.

FIG. 32 shows the remaining assembly process. Aspect 1401 is the same aswas shown in FIG. 31. Aspect 1402 illustrates the second support plate609 installed together with the fine screening material 606 and theadhesive dots 607 for attaching the membrane. Aspect 1403 shows theapplication of the membrane 1101 and the spacers 750A as discussedearlier.

FIG. 33 shows an alternate spacer design 1501 that also integrates wires1503 and a side cover 1502. The integral spacers 1501 can be stackedvertically around the membrane plates 1504 and provide the side seal forthe air flow, thus eliminating the need for a separate side cover 309 aswas shown in for example FIG. 300. The integral spacers 1501 could be aplastic material molded over the wires 1503 or alternatively a meshcould be over-molded as well.

FIG. 34 shows a detail of the bottom corner of FIG. 33. The detail alsoillustrates that it is possible to design a feature 1551 into theintegral spacer 1501 that provides a spring tension to the wires 1503.The spring feature 1551 helps ensure that the wires 1503 stay properlytensioned through different temperatures so that sagging or vibration inthe wires is inhibited.

FIG. 35 illustrates a surface turbulator as described in the prior art.An air stream 1555 is directed into a channel between two surfaces 1552,which can be membranes. The surface turbulators 1553 are placed atdistances typically 10 to 15 times the width of the channel atalternating sides of the channel. The surface turbulator causes smalleddies or vortices 1554 behind the turbulator which allows a largeramount of molecules in the air stream to be directed towards themembrane surfaces. However, the surface turbulators also cause a smallarea 1556 that is covered by the turbulator and is thus inactive fortransport of molecules through the membrane.

FIG. 36 shows a surface turbulator that uses the membrane itself tocreate eddies and vortices in the air stream. Since the membrane isrelatively thin, it is possible to form the screen 606 in such a waythat it holds the membrane at an acute angle to the air stream as isillustrated by element 1559. The support surface 609 can also be formedto create a ridge 1557, which then in turn forms a ridge in the screen606. It is also possible to adhere a separate material 1558 to thesupport surface 609 rather than forming the support material itself. Theadvantage of these methods is that the desiccant that is running in thescreen material 606 is now forced to stay close to the membrane 1552,which enhances the interaction between the air stream and the desiccantstreams. As can be seen from the figure, by forming the membrane overthese ridges, the surface area is increased and thus the efficiency ofthe system is improved as well.

FIG. 37 shows a turbulator that is able to generate a counter-rotatingair flow in a narrow air channel. The turbulator is also able to supporta membrane structure such as is shown in FIG. 78 and is easilymanufacturable, for example using injection molding technology. In thefigure, an air stream 1556-3 is directed to the turbulator structure.The structure is clamped in a narrow slot, for example in-between twomembrane surfaces. The top of the turbulator structure 1556-1 contacts amembrane or surface and is not shown. The bottom of the turbulatorstructure 1556-2 contacts a second membrane or surface and is also notshown. When the air stream 1556-3 reaches the turbulator, a section ofthe air stream 1556-4 contacts a wall 1556-6 that is placed at an angleto the air stream. The wall 1556-6 progressively gets shorter in thedownstream direction. As a result the air stream 1556-3 is forced into arotational motion as shown by air stream 1556-4. Furthermore an optionalobstruction 1556-7 forces the air stream back to the opposite directionthat wall 1556-6 was forcing the air stream in. As a result, the airstream is coerced into a right-handed rotation. Similarly a section ofthe air stream 1556-5 that is a small distance away from air stream1556-4, contacts a wall 1556-9 that is placed at an angle to the airstream, but in the opposite angle of wall 1556-6. Again, this wallslopes down in the direction of the air stream. As a result the airstream 1556-5 is forced into a rotation over the wall. Again an optionalobstruction 1556-8 forces the air stream in the other direction,resulting in a left-handed rotation of the air stream. The two streamscombine to a counter-rotation air stream behind the turbulator as isshown by air streams 1556-4 and 1556-5.

FIG. 38 shows an alternate construction for a half-membrane platestructure 1560. The support plate 609 as discussed earlier now has anover-molded spacer 1561. The spacer 1561 also acts as a side seal forthe air flow similar to FIG. 33. The membrane 1562 covers a thin screen1563.

The exploded view in FIG. 39 shows that the membrane 1562 is placed overthe thin screen 1563. The structure can be manufactured with simplemanufacturing operations such as die-cutting, over-molding, stencilprinting and roll-to-roll assembly processes.

FIG. 40 illustrates how two half-plates 1560 can be connected by usingthe seal arrangement from FIG. 1300. The main seal 1301 contains thecooling fluid. The desiccant supply seal 1302 and the desiccantcollection seal 1303 complete the assembly. After connecting the twohalf-plates as shown in the figure, multiple plates can be stacked tocreate a complete block of plates.

FIG. 41 shows an air-turbulating netting material that can also providemechanical support to the membrane structure in a half-plate aspect ofthe design. Since the membrane is relatively thin as mentioned above(˜20 μm), several techniques need to be employed to ensure that themembrane does not release from the support structure and enter into theair-stream. As shown in FIG. 700 a negative siphoning pressure in theliquid desiccant stream can help ensure that the membrane 603 stays flatagainst the support screen 606. Adhesive dots 607 ensure that the screenand the membrane stay in place. FIG. 41 shows an alternative air meshsupport structure 1572 to the adhesive dots 607. The air mesh supportstructure 1572 has two functions: it provides a level of turbulentmixing of the air stream and it contacts the membrane to keep it againstits support plate. The edge and liquid path seals 1502 were discussedearlier in FIG. 33.

FIG. 42 shows a detail cut-out of FIG. 41 wherein two membranesconnected to two 3-way membrane plates are supported by anair-turbulating netting 1572. The membranes 603 are contacted by the airmesh support structure 1572 from the air-gap side and by the screenmaterial 606 from the liquid desiccant side. A 3-way heat exchanger(which utilizes air, liquid desiccant, and a cooling fluid) would alsohave a water turbulating mesh 608 and a water sealing structure 1302 asshown earlier. Furthermore the support plates 609 provide mechanicalisolation between the liquid desiccant running through the screen 606and the cooling fluid running through the plate mesh 608.

FIG. 43 shows a similar detail to FIG. 42 wherein two membranesconnected to two 2-way membrane plates are supporting by anair-turbulating netting. In a 2-way membrane heat exchanger (air anddesiccant without a cooling fluid), the same air mesh support structure1572 can be deployed. The cooling fluid layer is simply eliminated fromthe plate structures.

FIG. 44 shows an embodiment of an air turbulating netting wherein thenetting also incorporates support structures designed to keep membranesmechanically in place as well as a set of spacers meant to keep the airstream contained to a slot between two membrane plates. The shape of thesupport structures can be designed to generally minimize the area loston the membrane while still achieving good support. Likewise, the shapeof the “wires” between the support structures can be designed tooptimize the air turbulence and mixing. The edge spacers 1502 aredesigned to provide one or more fluid connections between stacks ofmembrane plates. The air turbulating netting can be manufactured withmany different techniques such as forming, injection molding or othercommon manufacturing steps. By making the air turbulating netting from aflexible material such as EPDM, the netting remains elastic and cansupply a force to the membranes.

FIG. 45 shows how the air turbulating netting can support a membranestructure that is rolled into a cylindrical structure. Detail “A” showsa 2-way heat exchanger plate structure. Detail “B” shows a 3-way heatexchanger plate structure. By selecting flexible materials for thedesiccant mesh 606 and air turbulating netting, the structure can berolled into a multilayer cylindrical structure. Forces (represented bythe arrows 1576) constrain the rolled up structure. Supply and drainbulkheads 1575 provide for the fluid connections for the cooling fluidsand desiccant. The air stream is perpendicular to the plane of thefigure and is directed to only run through the rolled up structure.Detail “A” shows the rolled up structure for a 2-way air to desiccantheat exchanger, whereas detail “B” shows the rolled up structure for a3-way air, desiccant and cooling fluid structure.

FIG. 46 shows how the air turbulating netting can support a flatmembrane structure for a 3-way heat exchanger plate structure. Thestructure shown in the figure contains five 3-way liquid desiccantplates in the design of FIG. 10. Endplates 1578 are providing a force1577 on the five plates and the six air mesh support structures. Theassembly shown reduces the need for adhesives and the adhesive dots 607and 620 from FIG. 10 can be eliminated.

FIG. 47 shows how the air turbulating netting can support a flatmembrane structure for a 2-way heat exchanger plate structure. Thestructure shown in the figure contains five 2-way liquid desiccantplates. Endplates 1578 are providing a force 1577 on the five plates andthe six air mesh support structures. The assembly shown reduces the needfor adhesives.

In FIG. 48 a thermo-formed, die-cut support plate 1581 is shown. Thefunction of the support plate 1581 is identical to that of support plate609 in FIG. 10, however both the diamond mesh 608, the wicking fabric orscreen material 606 and the desiccant and cooling fluid supply and drainchannels (labeled 611, 612, 613 and 614 in FIG. 10) have been integratedinto the mold design. The desiccant supply channel 611 allows thedesiccant to run along the desiccant header 1585. The desiccant exitsthe header 1585 through the holes 1108 and can run on the outside of thesupport plate 1581. Desiccant collection holes 1103 allow the desiccantto re-enter the support plate and run through the desiccant drain header1584 to exit at drain 614. Similar to FIG. 10, the cooling fluid entersthe support plate through opening 614, and exits at the top of the plateat 612. Feature 1582 is a formed-in feature that functions like thediamond mesh shown in earlier figures. The feature 1582 can be formed inmany different ways, but should accomplish three main functions: 1) setthe distance between two support plates, 2) create turbulent mixing inthe cooling fluid while maintaining uniform cooling fluid flow patterns,and 3) provide a bonding surface to a second support plate.

The small features 1583 are raised slight above the surface of thesupport plate into the direction of the desiccant. These featuresprovide for a similar function as the wicking fabric or screen material606 as was shown in FIG. 10. The features provide for mixing of thedesiccant, they allow the membrane (not shown) to be bonded to thesupport plate and they set a uniform, firm distance between the membraneand the support plate so that uniform heat- and water vapor transportoccur. There are many possible configurations of the feature 1583possible to achieve these objectives.

FIG. 49 shows how two support plates from FIG. 48 can be attached backto back to provide a full plate structure. For clarity the two platesare shown separated a small distance. The feature 1582 on support plate1581 is mated to a similar feature 1587 on support plate 1586. When thetwo support plates are joined together, a full desiccant supply header,a desiccant drain header and a cooling fluid section are formed. Thefeatures 1582 and 1587 touch in numerous places creating a convolutedpath for the cooling fluid flow.

FIG. 50 shows the two joined plates. In the figure one of the plates hasbeen shown transparently so that the overlapping features 1582 and 1587can be seen to allow for fluid passage, turbulent mixing and a soliddistance between support plates.

FIG. 51 finally shows a detail back-side view of the bottom-left cornerof the support plate 1581 as was shown in FIG. 48. The small features1583 protrude into the desiccant area by typically 0.5 mm. The coolingfluid features 1582 protrude into the cooling fluid area, by typically1.5 to 2.0 mm. The cooling fluid supply port 613 is typically connectedon the desiccant side by a compliant spacer as was shown in FIG. 14.Desiccant is collected through the ports 1103 into the header 1584 andeventually drains through ports 614.

FIG. 52 shows an arrangement of the seals involved in the plate design609 of FIG. 10. As discussed prior the liquid desiccant 1591 entersthrough port 611, and runs inside the seal area 1304. The desiccantexits the seal area 1304 through the weeping holes 1108 and is containedby the membrane edge seal 1102. At the bottom of the membrane plate thedesiccant seal 1102 drives the desiccant into the plate through thedrain holes 1103, after which the lower desiccant seal 1303 drains thedesiccant through port 614. The cooling fluid 1592 enters the plate atport 613, and runs upward until it exits at port 612.

FIG. 53 shows an alternate arrangement that can be useful if additionalsensible cooling without dehumidification through the membrane isdesirable. The desiccant drain 613 is now located somewhere near theupper portion of the plate in such a way that the desiccant drains awayand the membrane seal 1102 (and the membrane—not shown) is now onlycovering the upper portion of the plate. As before, the desiccant 1591enters through port 611 and runs down the surface of the plate throughweeping holes 1108 and drains out through collection holes 1103 andthrough the drain port 613. The seal 1593 is now shaped in such a way asthe allow the cooling fluid 1592 to pass in the middle of the platethrough opening 1594. The desiccant collection seal 1595 is now split in2 portions with each side draining through a separate port 613.

FIG. 54 illustrates another embodiment of the arrangement of FIG. 53wherein the air stream 601 is directed primarily in a horizontal fashionacross the membrane across the membrane surface 1102. In section “A” themembrane is present with a desiccant behind the membrane and the air isdehumidified as well as cooled. Section “B” does not have a membrane andis therefore only providing additional sensible cooling to the airstream. The cooling fluid supplies 15967 and 1597 can now enter in forexample ports 612 and 613 and the fluid channel 1598 can be shaped insuch a way as to provide a counter-flow to the air stream 601. Theadvantage of this arrangement is that the cooling section “B” is actingon air that has already been dehumidified and therefore no condensationwill occur in section “B”.

FIG. 55 illustrates a 2-way liquid to liquid heat-exchanger that usessimilar concepts to the ones described above. Two main reinforced coverplates 1601 and 1602 contain a stack of plastic plates 1603. Liquidsupply ports 1604 and 1606 and liquid drain ports 1605 and 1607 providea counter-flow arrangement.

FIG. 56 shows the 2-way heat exchanger from FIG. 55 with one of thecovers removed. The hole 1701 provides for a passage of liquid “A” thatflows up through a diamond mesh turbulator 1707 and into the drain hole1703. A main seal 1705 provides separation between the liquids “A” and“B” and the outside environment. As can be seen from the figure liquid“B” does not flow into the channel as the seal 1705 simply transports itto the next plate. As discussed under the 3-way heat exchanger, thediamond mesh turbulator 1707 provides two main functions: it sets thedistance between the support plates 1706 and creates turbulent liquidflow across the plates. FIG. 57 shows the 2-way heat exchanger from FIG.55 with an additional plate 1705 removed. As can be seen from the figurethe seal 1705 now circles the opposite set of holes so that the fluid“B” can flow through the diamond mesh turbulator 1707.

FIG. 58 shows the support plate 1706 which can be made similarly to thesupport plate 609 of the 3-way heat exchanger from a fiberglassreinforced plastic or a thermally conductive engineering plastic. Theseal 1705 can again be made with an adhesive as discussed before forexample 3M 550 or 5200 polyurethane adhesives. Such adhesives can beapplied by hand or through a specifically designed adhesive robotsystem. A diamond mesh turbulator 1707 is applied inside the adhesiveseal as was shown in FIG. 56.

FIG. 59 and FIG. 60 show the alternating plates that make up the fullplate stack 1603 as was shown in FIG. 55.

FIG. 61 illustrates a 2-part membrane plate module wherein one part ismade from a flexible material such as a polyurethane or EPDM rubber.Since membrane modules can be subject to higher temperatures, theassembly of the module is critical to ensure that temperature gradientsdo not cause materials to crack or adhesive bonds to fail. Oftentimesthose failures are observed when plastics (which tend to have largethermal expansion coefficients) expand and generate stresses on bondsand adhesives. Membranes are often “potted” (meaning a liquid plastic isused to create seals between various components) but such pottingmaterials once they cure can also easily fail. In liquid desiccant heatexchangers, this is particularly of importance on the regenerator, andto a lesser extent on the conditioner. Furthermore, supplying liquidsevenly on opposite sides of non-internally cooled thin plates isoftentimes difficult. A 2-part structure where one portion is made froma pliable material such as EPDM or polyurethane is significantly moreforgiving.

FIG. 61 shows a module with 2 distinct air passages 2006 and 2011 andtwo distinct sections 2007 and 2008. A front-side outer membrane 2001 isattached to a semi-rigid plate 2015 (which is more easily seen in FIG.62). The liquid header 2007 at the top of the structure forms, combinedwith a flexible EPDM or similar material section 2008, a supply fluidchannel 2005 for the outer membrane and a second fluid supply channel2004 for the inner membranes 2012. It is worthwhile observing that thereare two ports 2005 and 2004 on either end of the structure. This isbecause the fluids should preferably be distributed evenly across thesurface of the membrane. It is very difficult to provide a uniform layerif the fluid gets too far away from the entry port. In practice adistance of about 400 to 500 mm between the two ports is achievable, butbeyond that the middle of the membrane would become fluid starved.Having only one port in the header could therefore limit the width ofthe plate to about 300 mm. It should be clear that additional portscould be added to the header if desired to increase the width of the2-plate structure to over 500 mm.

The liquids are drained through the drain 2002 for the inner membranesand the drain 2003 for the outer membranes. The flexible material 2008can optionally also provide an edge seal 2009 to guide the air 2006 in avertical aspect through the flexible material 2008, similar to thematerial 602 in FIG. 10 while also providing a certain amount ofturbulent air mixing. The flexible component 2008 serves severalfunctions: it provides a pliant interface between stacks of plates 2007;it provides passages for liquids between stacks of plates 2007; itprovides an air channel edge seal 2009; it provides support for theouter membranes between stacks of plates 2007; and it provides ameasured amount of air turbulence in the air channel. FIG. 62 shows the2-part plate stack of FIG. 61 with the membrane 2001 removed. The rigidsupport plate 2015 is clearly visible with liquid supply holes 2013(which serve to provide a liquid behind the membrane 2001) and liquiddrain holes 2014. The figure shows how a liquid 2014 enters the 2-partstructure 2007/2008 at the top of the figure, runs into the fluidheader, through a supply hole 2013 and over the outer surface of thesupport plate 2015. As can be seen in the figure, the support plate 2015can be outfitted with various features to adhere the membrane 2001 andalso to provide turbulent flow of the fluid as discussed in thedescription of FIG. 10.

FIG. 63 shows the rear-side of the 2-part plate stack of FIG. 61. Arear-side outer membrane 2016 is being supported by the flexiblestructure 2008 which also contains supports 2017 for the rear-outermembrane 2016.

FIG. 64 shows a detailed aspect of the lower left corner of FIG. 63. Thefigure shows the front outer-membrane 2001 attached to the support plate2015. One of the two inner membranes 2012 is also shown. The secondaryair stream 2011 is being turbulated by the membrane support structure2010. It is possible to make the inner membrane support structure 2010from a similar material as the outer membrane support structure 2008.The structure 2010 also contains a membrane edge seal 2021 which is setup in a way such that liquids between the inner membrane 2012 and thesupport plate 2015 can drain into the fluid drain holes 2025 (shown inFIG. 65). The lower fluid header 2007 is similar in construction to theupper fluid header or can be identical. The fluid headers can be madefrom an extruded plastic such as ABS or a flexible plastic such as EPDM.The header end-cap has been shown removed for clarity. The innermembrane fluid drain channel 2022 and the outer membrane fluid drainchannel 2023 are also visible in the figure. The figure also shows theturbulator 2019 which has been made part of the flexible structure 2008.Membrane support pads 2020 keep the membrane 2016 in place. It should beclear that the support pads 2020 are serving the same function as thesupports 1572 in FIG. 41. It is also clear that the membranes can beheld against the support plate 2015 by a siphoning effect as discussedunder FIG. 700.

FIG. 65 shows the same aspect as FIG. 64 with the inner membrane 2012and the inner membrane support structure 2010 removed. The figure alsoshows the membrane support features 2015A used for either attaching themembranes and for diverting the fluid flows or both. Furthermore thefluid path 2024 for the fluid behind the inner membrane is shown. Thefluid drain holes 2025 in the lower header are also visible.

FIG. 66 shows the 2-part membrane plate assembly from FIG. 61 in an“exploded view” aspect. The inner membrane support structure 2010 hastwo inner membranes 2012 on either side of the structure. The upper andlower fluid headers 2007 supply and drain fluid from the membranestructures for both the inner and outer membranes. Support plates 2015provide rigid support and features for turbulating the fluids. The outermembranes 2001 and 2016 are attached on the outside of the supportplates 2015. The flexible structure 2008 finally completes thestructure.

FIG. 67 shows a close-up view of the upper fluid header with the fluidsupply channel 2026 for the outer membranes and the fluid supply channel2027 for the inner membranes visible. The outer membranes receive fluidsthrough the supply holes 2029 and the inner membranes receive fluidthrough the supply holes 2028.

FIG. 68 illustrates the fluid supply paths for the outer membrane 2029as well as the fluid path 2033 for the inner membrane.

FIG. 69 illustrates the fluid drain path 2032 for the outer membrane aswell as the fluid drain path 2024 for the inner membrane. Drain holes2025 and the fluid channel 2022 for the inner membranes are shown as arethe lower drain holes 2031 for the outer membranes on the fluid channel2023.

FIG. 70 shows a stack of multiple 2-plate structures arranged into across-flow air treatment module. Liquids are supplied at the top of thestructure through two ports 2005 for achieving more uniform fluiddistribution across the outer membranes. Likewise the two ports 2004provide even fluid distribution across the inner membranes. Drain ports2002 and 2003 provide drainage for the inner membranes and outermembranes respectively. Notice that the fluids behind the inner andouter membranes can be different or identical. For example, one of thefluids could be a desiccant and the other could be plain water, orseawater or waste water. Other fluids are also possible. As discussedbefore, the primary air stream 2007 can be in an downward or in anupward aspect and the cross-flow air stream 2010 can enter the modulefrom either side.

FIG. 71 demonstrates an application of the membrane module of FIG. 70wherein the primary air stream 2006 comprising outdoor air flowsgenerally vertically through the module and is partially diverted bydiverter 2503 to become part of the secondary air stream flowinggenerally horizontally through the module. An additional secondary airstream 2501 which can, e.g., also be an outside air stream is applied aswell. By now providing a liquid desiccant through ports 2005 the primaryair stream 2006 is dehumidified through the outer membranes. If water isprovided through the ports 2004, the secondary air stream will cause anevaporative cooling effect on the backside of the support plates 2015shown earlier. This indirect evaporative cooling effect removes thelatent heat as well as sensible heat from the primary air stream. Thiscooling effect then in turn improves the dehumidification in the primarychannel which the gives a larger cooling effect in the secondary channelas a self-reinforcing system. The end plates 2502 and 2504 providesupport and mounting of the plate stacks as well as a convenientinterface for the fluids

FIG. 72 shows the system of FIG. 71 with the end plate 2504 removed. Ascan be seen in the figure, the diverter 2503 is diverting a portion 2507of the air in the channel. The diverter can be made from a flexible oradjustable material or parts so that the diverted air portion can bevaried for example by moving the intake opening 2506 or the secondaryair mixing ratio by moving section 2505. This allows the secondary airstream composition to be varied; for example in hot weather that is dry,there may be little need to use any of the primary dry air.

FIG. 73 shows a detail of the lower left corner of FIG. 72, clearlyshowing how the primary air path in the vertical slots is changed tobecome the horizontal air path in the secondary air stream.

FIG. 74 shows an alternate embodiment of the system in FIG. 71. whereina portion 2507 of the primary air stream 2006, after it has been treatedby the membrane module plates 2513 is directed in ducts 2510 to flow up2508 and to the top of the membrane module and where it is turned to ahorizontal secondary air stream in such a way as to run in the alternatechannels formed by the horizontal slots. The advantage of thisarrangement is that the treated dry air 2509 is now mixed at the mostadvantageous location near the top of the secondary channel, where ithas the greatest cooling effect on the primary air stream 2006. Thesecondary air stream 2501 now provides cooling near the bottom of themembrane plates 2513. The exiting air 2511 is then combined with theexiting air 2512 that is the result of the diverted air flow 2507.Although more complicated as a duct work, the advantage of redirectingthe air flow near the top of the membrane panels results in a moreefficient system. It will be clear to those skilled in the art that theprimarily air flow 2006 and secondary air flow 2501 can be switched sothat the primary air stream is horizontal and the secondary air streamis vertical (either flowing up or down as the case may be).

FIG. 75 illustrates an alternate embodiment of the 2-part plate stack ofFIG. 61. In this case the vertical air flow membrane support structure2008 has been modified to allow for a horizontal air flow. The newmembrane support structure 2601 again is constructed from a compliantmaterial such as Polyurethane or EPDM rubber. It also can provide forair turbulation and membrane support features as well as an edge sealand liquid passages.

FIG. 76 shows an “exploded view” of the 2-part plate stack of FIG. 75.The structure is essentially unchanged from that of FIG. 66 with theexception of the membrane support structure 2601 that now provides forhorizontal air flow.

FIG. 77 shows a detail of the lower left corner of FIG. 76. The frontouter-membrane 2001 attaches to the support plate 2015, which in turn isadhered to the lower header 2007. The membrane support structure 2010provides support for the inner membranes 2012. Fluid drains 2025 for theinner membranes allow fluids to drain into channel 2002. Drain holes2031 in the support plate 2015 allow the outer membranes 2001 and 2016to drain into the lower fluid channel 2003.

FIG. 78 now illustrates a membrane module wherein air in a horizontalaspect is contacted by fluids behind the membranes. Ports 2005 providefluids to the outer membranes and ports 2004 provide fluids to the innermembranes. Ports 2002 drain the fluids from the inner membranes andports 2003 drain the outer membranes. It should be clear that if thefluids provided to ports 2005 and 2004 are identical (for example theyboth contain the same desiccant) then the fluid channels and supplychannels can be combined into a single channel. This would simplify themembrane modules construction Likewise it is easy to envision astructure that has more than 2 fluids exposed to the air stream byemploying 3 or 4 separate supply and drain passages.

FIG. 80 illustrates a cross sectional view of the module described underFIG. 2000, with similar construction details as was shown in FIGS.2100A, 2100B, 2200A, 2200B, 2300A, and 2300B, wherein the support plate2015 has been modified so that it can wrap around a refrigerant line2801 as is shown by the bulge in the plate 2802. Refrigerants aretypically operating at high pressures which can vary from 200 to 600psi, necessitating the use of metal lines. The refrigerant lines 2801can provide cooling (or heating as the case may be) to the desiccant bythermal conduction through the support plate 2015. The liquid desiccantthat is running behind the membranes 2012 and 2016 is highly corrosiveso that direct contact with the metal refrigerant lines is undesirable,unless the refrigerant lines are made of a highly inert metal liketitanium which can be cost prohibitive. By wrapping the support plate2015 around the refrigerant lines 2801, a good thermal contact can beachieved, without the need for a titanium pipe and simple copper tubing(which is commonly used for refrigerants) can be employed. It is alsopossible to construct the refrigerant lines at an angle to the airstream so that the “bulge” in the membrane 2802 functions similarly tothe surface turbulators as was shown in FIGS. 35 and 1555B. Therefrigerant lines allow for direct cooling of the desiccant and can berepeated every several inches to prevent the desiccant from heating uptoo much as it is running from the top to the bottom of the membraneplate. The advantage of this approach is that the air can now bedehumidified and cooled with a conventional vapor compression system,rather than using indirect backside evaporative cooling as was shown forexample in FIG. 71.

Having thus described several illustrative embodiments, it is to beappreciated that various alterations, modifications, and improvementswill readily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to form a part of thisdisclosure, and are intended to be within the spirit and scope of thisdisclosure. While some examples presented herein involve specificcombinations of functions or structural elements, it should beunderstood that those functions and elements may be combined in otherways according to the present disclosure to accomplish the same ordifferent objectives. In particular, acts, elements, and featuresdiscussed in connection with one embodiment are not intended to beexcluded from similar or other roles in other embodiments. Additionally,elements and components described herein may be further divided intoadditional components or joined together to form fewer components forperforming the same functions. Accordingly, the foregoing descriptionand attached drawings are by way of example only, and are not intendedto be limiting.

1. A support structure for use in a heat exchanger in a desiccant airconditioning system, comprising: two molded support plates attached toeach other back-to-back; each support plate comprising an array ofintegrally-formed raised features on a front side thereof for providinga bonding surface for a membrane and for mixing or turbulating flow of aliquid desiccant flowing between the front side of the support plate andthe membrane; each support plate also comprising a plurality ofintegrally-formed raised features on a back side thereof for setting adistance from the other support plate, mixing or turbulating flow of aheat transfer fluid flowing between the support plates, and providing abonding surface for attaching the support plates; and each support platealso including one or more openings through which the liquid desiccantcan be introduced on the front side of the plate and one or moreopenings for collecting the liquid desiccant.
 2. The support structureof claim 1, wherein each support plate also includes one or moreopenings through which the heat transfer fluid can be introduced forflowing between the support plates and one or more openings forcollecting the heat transfer fluid.
 3. The support structure of claim 1,wherein the raised features on the back side of each support plateperiodically touch the raised features on the backside of the othersupport plate to form a convoluted path for flow of the heat transferfluid.
 4. The support structure of claim 1, wherein the raised featureson the front side of each support plate are configured to generallyevenly distribute liquid desiccant over the front side of the supportplate.
 5. The support structure of claim 1,wherein each support platecomprises a thermally conductive rigid plastic material.
 6. The supportstructure of claim 1, wherein the two molded support plates areidentically constructed.
 7. A two-way heat exchanger for transferringheat from a first liquid to a second liquid, comprising: a plurality ofplate assemblies in a generally parallel arrangement defining aplurality of channels, each between adjacent plate assemblies, saidchannels alternating between first and second channels for separate flowtherethrough of the first and second liquids, respectively, wherein eachplate assembly comprises a support plate utilizing a mesh turbulator formixing or turbulating liquid flowing through a channel defined saidsupport plate and a support plate in an adjacent plate assembly and forsetting a distance between the support plates, an inlet opening for flowof a liquid into said channel, an outlet opening for discharging liquidfrom said channel, and a seal structure for allowing passage of only oneof said first and second liquids through said channel.
 8. The two-wayheat exchanger of claim 7, wherein the mesh turbulator is molded in thesupport plate.
 9. The two-way heat exchanger of claim 7, wherein meshturbulator is a separate component from the support plate.
 10. Thetwo-way heat exchanger of claim 7, wherein the mesh turbulator comprisesa diamond mesh turbulator.
 11. The two-way heat exchanger of claim 7,wherein each turbulator comprises a plastic netting material.
 12. Thetwo-way heat exchanger of claim 7, wherein each support plate comprisesa thermally conductive rigid plastic material or a fiberglass-reinforcedplastic material.
 13. The two-way heat exchanger of claim 7, furthercomprising outer covers at opposite ends of the plurality of plateassemblies.
 14. The two-way heat exchanger of claim 7, wherein the firstand second liquids flow in generally opposite directions in adjacentchannels.
 15. A heat exchanger for use in a desiccant air conditioningsystem, comprising: a plurality of membrane-plate assemblies facing eachother in a generally parallel arrangement and being spaced apart todefine air gaps therebetween through which air to be treated by thedesiccant air conditioning system can flow, each of said membrane-plateassemblies comprising (a) a plate structure, and (b) two membranes, eachfacing an opposite side of the plate structure and spaced apart from theplate structure to define a gap therebetween through which a liquiddesiccant can flow, wherein each plate structure includes a metal heattransfer pipe to transfer heat to or from the liquid desiccant, saidmetal heat transfer pipe encapsulated by a non-corrosive material toprevent corrosion of the metal heat transfer pipe by the liquiddesiccant.
 16. The heat exchanger of claim 15, wherein the metal heattransfer pipe comprises a copper pipe.
 17. The heat exchanger of claim15, wherein the metal heat transfer pipe comprises a pressurizedrefrigerant line.
 18. The heat exchanger of claim 15, wherein the heattransfer pipe forms a bulge in the plate structure defining a turbulatorfor mixing or turbulating flow of the liquid desiccant.
 19. The heatexchanger of claim 15, further comprising a plurality of metal heattransfer pipes embedded in each plate structure.